Watchful eye

City avoids $500,000 in illegal discharge fines with real-time flow monitoring at more than 100 sites

OWNER: South Bend (Ind.) Wastewater DepartmentASSET: 20-square-mile combined sewer overflow (CSO) systemPROBLEM: Too many dry-weather sanitary sewer overflowsSOLUTION: Wirelessly monitor water levels at 110 sites — all 36 outfalls, every river crossing, retention basins, and pump stations in interceptor and trunk lines to maximize system capacity during all weatherCOST: $1.9 million for installation; $400,000 for CSONet equipment and a one-year subscription to the CSONet systemFUNDING: $1.2 million grant and $1.7 million low-interest loan in Clean Water State Revolving Fund stimulus fundingPROJECTED SAVINGS: $110 million to $150 million in construction costs and nearly $190,000 in annual operating and maintenance costs of the combined sewerDRY-WEATHER OVERFLOWS SINCE INSTALLATION:2008: 292009: 102010: 2

THE LATEST: In February 2009 South Bend's Wastewater Department became the first in North America to monitor combined sewer assets in real time, making the city's the most densely monitored system in the country.

A local co local company — EmNet LLC — has been testing a system called CSONet developed with the University of Notre Dame and Purdue University.

CSOnet is a network of monitoring points called instrument nodes (INodes) and data acquisition points called “gateways.” An INode is a composite fiberglass manhole cover (made by GMI Composites) rated to the American Association of State Highway and Transportation Officials' HS-20 highway strength standard that contains a battery-operated computer and antenna. It gathers data from a sensor mounted in the sewer and transmits it via radio frequency to a gateway.

To date, the department's used the monitoring data to create reports and learn of potential illegal dry-weather overflows when its SCADA interface transmits alarms to the CSO operation managers.

The two-person crew that was inspecting the system for potential overflows has been freed up to clean 2,000 additional catch basins annually and triple the amount of manhole inspections from 2,500 in 2007 to 8,000 in 2009. That's $189,000 in operations and maintenance benefits without a single layoff.

Finally, the department was able to establish a baseline flow for each site. Knowing the normal flow condition now allows managers to respond before an overflow occurs. If the water level rises above the baseline flow, the SCADA system sends an alarm to managers.

“It's allowed the city to see what's happening in real time with both early detection and prevention,” says Patrick Henthorn, assistant city engineer.

Now the department's moving on to the next step: controlling the system in real time.

Nine Red Valve Co. Inc. pinch valves are being installed on a new throttle line to maximize inline and offline storage and control flows into the treatment plant. Construction is expected to be complete by the end of October.

“CSONet will serve as a tool going forward to help manage flows during wet weather events in addition to monitoring daily flows,” Henthorn adds.